Reconfigurable filters in multiplexer

Abstract

A filter device for multi-band wireless communication includes a first circuit characterized by a first pass-band from a first frequency to a second frequency; a second circuit characterized by a second pass-band from a frequency no smaller than the first frequency to a third frequency, the third frequency being no higher than the second frequency but higher than the first frequency; a third circuit characterized by a third pass-band from a fourth frequency to a frequency no greater than the second frequency, the fourth frequency being no smaller than the first frequency but smaller than the second frequency; and a switch configured to connect the first circuit either to the second circuit to reconfigure a first filter with the second pass-band or to the third circuit to reconfigure a second filter with the third pass-band.

What is claimed is: 
     
         1 . A filter device for multi-band wireless communication comprising:
 a first circuit characterized by a first pass-band from a first frequency to a second frequency, the second frequency being greater than the first frequency;   a second circuit characterized by a second pass-band from a frequency no smaller than the first frequency to a third frequency, the third frequency being no higher than the second frequency but higher than the first frequency;   a third circuit characterized by a third pass-band from a fourth frequency to a frequency no greater than the second frequency, the fourth frequency being no smaller than the first frequency but smaller than the second frequency; and   a switch being configured to connect the first circuit either to the second circuit to reconfigure a first filter with the second pass-band or to the third circuit to reconfigure a second filter with the third pass-band, wherein at least one of the second pass-band and the third pass-band is narrower than the first pass-band.   
     
     
         2 . The device of  claim 1  wherein the first circuit comprises a first rejection-band below a fifth frequency and a second rejection-band above a sixth frequency, the fifth frequency being smaller than the first frequency, the sixth frequency being higher than the second frequency. 
     
     
         3 . The device of  claim 2  wherein the first filter comprises a third rejection-band below a seventh frequency and a fourth rejection-band above an eighth frequency, the seventh frequency being aligned with the fifth frequency, the eighth frequency being greater than the third frequency but smaller than the sixth frequency. 
     
     
         4 . The device of  claim 2  wherein the second filter comprises a fifth rejection-band below a ninth frequency and a sixth rejection-band above a tenth frequency, the ninth frequency being smaller than the fourth frequency but greater than the fifth frequency, the tenth frequency being aligned with the sixth frequency. 
     
     
         5 . The device of  claim 3  wherein the first circuit comprises a plurality of first resonators coupled in series in a transmission line and a plurality of second resonators coupled in parallel with the transmission line, each first resonator being characterized by a respective anti-resonance frequency associated with the sixth frequency, each second resonator being characterized by a respective resonance frequency associated with the fifth frequency. 
     
     
         6 . The device of  claim 5  wherein each of the first resonator and the second resonator comprises a film bulk acoustic resonator (FBAR). 
     
     
         7 . The device of  claim 5  wherein the second circuit comprises a plurality of third resonators coupled in series in a transmission line and a plurality of fourth resonators coupled in parallel with the transmission line, each third resonator being characterized by a respective anti-resonance frequency associated with the eighth frequency, each fourth resonator being characterized by a respective resonance frequency associated with the seventh frequency, each of the third resonator and the fourth resonator comprising a film bulk acoustic resonator (FBAR). 
     
     
         8 . The device of  claim 7  wherein the third rejection band comprises at least 40 dB loss for frequencies smaller than the seventh frequency, attributed to an aggregation of each peak impedance contribution from each fourth resonator and second resonator at the respective resonance frequency with the seventh frequency being aligned to the fifth frequency. 
     
     
         9 . The device of  claim 7  wherein the fourth rejection-band comprises at least 40 dB loss for frequencies greater than the eighth frequency, attributed to an aggregation of each peak impedance contribution from each third resonator and first resonator at the respective anti-resonance frequency. 
     
     
         10 . The device of  claim 4  wherein the third circuit comprises a plurality of fifth resonators coupled in series in a transmission line and a plurality of sixth resonators coupled in parallel with the transmission line, each fifth resonator being characterized by a respective anti-resonance frequency associated with the tenth frequency, each sixth resonator being characterized by a respective resonance frequency associated with the ninth frequency, each of the fifth resonator and the sixth resonator comprising a film bulk acoustic resonator (FBAR). 
     
     
         11 . The device of  claim 10  wherein the fifth rejection-band comprises at least 40 dB loss for frequencies smaller than the ninth frequency, attributed to an aggregation of each peak impedance contribution from each sixth resonator and second resonator at the respective resonance frequency. 
     
     
         12 . The device of  claim 11  wherein the sixth rejection-band comprises at least 40 dB loss for frequencies greater than the tenth frequency, attributed to an aggregation of each peak impedance distribution of each fifth resonator and first resonator at the respective anti-resonance frequency with the tenth frequency being aligned to the sixth frequency. 
     
     
         13 . The device of  claim 3  wherein the first filter comprises a fourth pass-band from an eleventh frequency to a twelfth frequency, a seventh rejection-band below a thirteenth frequency, and an eighth rejection-band above a fourteenth frequency, the eleventh frequency being higher than the first frequency, the twelfth frequency being lower than the second frequency, the thirteenth frequency being higher than the fifth frequency but the seventh rejection-band being deeper in rejection than the first rejection-band, the fourteenth frequency being lower than the sixth frequency but the eighth rejection-band being deeper in rejection than the second rejection-band. 
     
     
         14 . A reconfigurable filter device comprising:
 a first circuit characterized by a first pass-band from a first frequency to a second frequency, the second frequency being higher than the first frequency;   a second circuit characterized by a second pass-band from a frequency no smaller than the first frequency to a third frequency, the third frequency being no higher than the second frequency but higher than the first frequency;   a third circuit characterized by a third pass-band from a fourth frequency to a frequency no greater than the second frequency, the fourth frequency being no lower than the first frequency but lower than the second frequency;   a switch comprising an input port coupled to the first circuit, a first output coupled to the second circuit, and a second output port coupled to the third circuit, the switch being configured to receive a first signal filtered with the first pass-band through the first circuit at the input port and deliver to the first output port for reconfiguring a second signal filtered with the second pass-band through the second circuit, or directly to the second output port for reconfiguring a third signal filtered with the third pass-band through the third circuit; and   a fourth circuit coupled in parallel to the switch between the first circuit and the second circuit or the third circuit and configured to enforce rejection-bands for the second signal or the third signal.   
     
     
         15 . The device of  claim 14  wherein the first circuit comprises a plurality of first resonators coupled in series in a transmission line and a plurality of second resonators coupled in parallel with the transmission line, the plurality of second resonators resulting in a first rejection-band below a fifth frequency, the plurality of first resonators resulting in a second rejection-band above a sixth frequency, the fifth frequency being lower than the first frequency, the sixth frequency being higher than the second frequency. 
     
     
         16 . The device of  claim 15  wherein the second circuit comprises a plurality of third resonators coupled in series in a transmission line and a plurality of fourth resonators coupled in parallel with the transmission line, the second circuit combined with the first circuit producing a first filter with the second pass-band, the plurality of fourth resonators and the plurality of second resonators providing the first filter with a third rejection-band with higher loss than the first rejection-band below a seventh frequency, the plurality of third resonators and the plurality of first resonators providing the first filter with a fourth rejection-band with higher loss than the second rejection-band above an eighth frequency, the seventh frequency being aligned with the fifth frequency, the eighth frequency being higher than the third frequency. 
     
     
         17 . The device of  claim 16  wherein the third circuit comprises a plurality of fifth resonators coupled in series in a transmission line and a plurality of sixth resonators coupled in parallel with the transmission line, the third circuit combined with the first circuit producing a second filter with the third pass-band, the plurality of sixth resonators and the plurality of second resonators providing the second filter with a fifth rejection-band with higher loss than the first rejection band below a ninth frequency, the plurality of fifth resonators and the plurality of first resonators providing the second filter with a sixth rejection-band with higher loss than the second rejection-band above a tenth frequency, the ninth frequency being lower than the fourth frequency, the tenth frequency being aligned with the sixth frequency. 
     
     
         18 . The device of  claim 17  wherein the fourth circuit comprises a capacitor, or an inductor, or a resonator configured to reconfigure the first or second filter with increased rejection loss by shifting the anti-resonance frequency of one of the first resonators in the first circuit. 
     
     
         19 . The device of  claim 16  wherein the first filter is alternatively characterized by a fourth pass-band that is configured to be narrower than and within the first pass-band, a seventh rejection-band below an eleventh frequency that is higher than the fifth frequency, and an eighth rejection-band above twelfth frequency that is lower than the sixth frequency, the seventh rejection-band being deeper in rejection than the first rejection-band, the eighth rejection-band being deeper in rejection than the second rejection-band. 
     
     
         20 . A reconfigurable filter device comprising:
 a circuit comprising a first plurality of resonators in series and shunt circuitry characterized by a first pass-band from a first frequency to a second frequency, a second plurality of resonators in series and shunt circuitry characterized by a second pass-band from a frequency no smaller than the first frequency to a third frequency, a third plurality of resonators in series and shunt circuitry characterized by a third pass-band from a fourth frequency to a frequency no greater than the second frequency, and a capacitor coupled between the first plurality of resonators and the second plurality of resonators, the third frequency being lower than the second frequency but higher than the first frequency, the fourth frequency being higher than the first frequency but lower than the second frequency; and   a switch configured to couple to the circuit to either connect the first plurality of resonators to the second plurality of resonators to reconfigure a first filter with the second pass-band and deeper rejection-bands or connect the first plurality of resonators to the third plurality of resonators to reconfigure a second filter with the third pass-band and deeper rejection-bands.